Conventionally, there has been widespread use of trigger sprayers as pieces of equipment that are attached to containers for causing liquid inside the containers to be ejected or sprayed.
In principle, such a trigger sprayer includes a piston and a cylinder and causes liquid inside the cylinder to be sprayed through a nozzle by moving the piston to apply pressure to the liquid.
Such trigger sprayers are classified into several types according to how their pistons move.
These types include, for example, a type of trigger sprayer whose trigger, provided in front, is pulled backward with a finger (see PTL 1).
Moving the trigger backward by squeezing it with a hand causes the piston to be depressed in step with the movement of the trigger to raise the pressure of liquid inside the cylinder.
This in turn causes the liquid to be sprayed with force through a nozzle part.
Further, there has been proposed a type of trigger sprayer including a main body and a trigger disposed above the main body, wherein liquid inside a cylinder is pressurized by pressing in a back end of the trigger downward and depressing a piston in step with the movement of the trigger.
Such a trigger sprayer includes an F valve on an upstream side of a passage and an S valve on a downstream side.
Specifically, the F valve is provided in a passage between a cylinder portion and a container, and the S valve is provided in a passage section between the cylinder portion and a nozzle part.
Liquid inside the container is pulled up into a cylinder through this F valve, and when pressurized, the liquid once pulled up into the cylinder is sent to the nozzle part through the S valve to be squirted out.
Incidentally, a conventional S valve 100 has not necessarily attained satisfaction from the point of view of the efficiency with which liquid flows.
FIG. 9 is an enlarged sectional view of a structure in the vicinity of an S valve in an example of a conventional trigger sprayer.
The S valve 100 includes a rod-like valve body 110 and a spinner 120, with a valve seat 121 supported by a back end of the spinner 120.
At normal times, the rod-like valve body 110 has its shoulder 111 brought into elastic contact with the valve seat 121 by a spring 130.
Application of pressure to the liquid causes the rod-like valve body 110 to move back against spring force, so that an interstice develops between the shoulder 111 and the valve seat 121.
After the S valve 100 has thus opened, the liquid flows downstream (toward a nozzle part) through this interstice.
However, whereas the liquid flows forward (downstream), the rod-like valve body 110 moves backward (upstream).
Therefore, since the liquid flows in a direction opposite to the direction that the rod-like valve body 110 moves, this constitutes a hindrance to the downward flow of the liquid, thus decreasing the efficiency with which the liquid flows.
This also adversely affects the efficiency with which the liquid squirts.